diff --git a/.github/actions/setup/action.yml b/.github/actions/setup/action.yml
index 1da9ab7f751..497d4ecdff7 100644
--- a/.github/actions/setup/action.yml
+++ b/.github/actions/setup/action.yml
@@ -34,18 +34,19 @@ runs:
         sudo add-apt-repository ppa:ubuntu-toolchain-r/test
 
         wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        sudo add-apt-repository 'deb http://apt.llvm.org/noble/ llvm-toolchain-noble-19 main'
+        sudo add-apt-repository 'deb http://apt.llvm.org/noble/ llvm-toolchain-noble-20 main'
 
         sudo apt-get update -y
         sudo apt-get install -y autoconf autoconf-archive automake build-essential ccache cmake curl fonts-liberation2 \
             gcc-14 g++-14 libcurl4-openssl-dev libegl1-mesa-dev libgl1-mesa-dev libpulse-dev libssl-dev \
-            libstdc++-14-dev lld-19 nasm ninja-build qt6-base-dev qt6-tools-dev-tools tar unzip zip
+            libstdc++-14-dev lld-20 nasm ninja-build qt6-base-dev qt6-tools-dev-tools tar unzip zip
 
         if ${{ inputs.toolchain == 'Clang' }} ; then
-          sudo apt-get install -y clang-19 clang++-19 clang-tools-19
-          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 100
-          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-19 100
+          sudo apt-get install -y clang-20 clang++-20 clang-tools-20
+          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-20 100
+          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-20 100
         fi
+
         sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 100
         sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 100
 
@@ -112,7 +113,7 @@ runs:
       run: |
         set -e
         brew update
-        brew install autoconf autoconf-archive automake bash ccache coreutils llvm@19 nasm ninja pkg-config qt unzip wabt
+        brew install autoconf autoconf-archive automake bash ccache coreutils llvm@20 nasm ninja pkg-config qt unzip wabt
 
     - name: 'Set required environment variables'
       if: ${{ inputs.os == 'Linux' && inputs.arch == 'arm64' }}
diff --git a/.github/workflows/js-artifacts.yml b/.github/workflows/js-artifacts.yml
index b1786f04f1c..56561bbb410 100644
--- a/.github/workflows/js-artifacts.yml
+++ b/.github/workflows/js-artifacts.yml
@@ -51,8 +51,8 @@ jobs:
       - name: Create build directory Ubuntu
         run: |
           cmake --preset Distribution_CI \
-            -DCMAKE_C_COMPILER=clang-19 \
-            -DCMAKE_CXX_COMPILER=clang++-19 \
+            -DCMAKE_C_COMPILER=clang-20 \
+            -DCMAKE_CXX_COMPILER=clang++-20 \
             -DENABLE_GUI_TARGETS=OFF
         if: ${{ matrix.os_name == 'Linux' }}
 
diff --git a/.github/workflows/js-benchmarks.yml b/.github/workflows/js-benchmarks.yml
index dccaa01ce6e..3951562c65f 100644
--- a/.github/workflows/js-benchmarks.yml
+++ b/.github/workflows/js-benchmarks.yml
@@ -37,9 +37,9 @@ jobs:
         shell: bash
         run: |
           sudo apt-get update
-          sudo apt-get install -y clang++-19 python3-venv
-          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 100
-          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-19 100
+          sudo apt-get install -y clang++-20 python3-venv
+          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-20 100
+          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-20 100
 
       - name: 'Download JS repl artifact'
         id: download-artifact
diff --git a/.github/workflows/lagom-template.yml b/.github/workflows/lagom-template.yml
index 31900d4c3ec..60edc42f941 100644
--- a/.github/workflows/lagom-template.yml
+++ b/.github/workflows/lagom-template.yml
@@ -71,8 +71,8 @@ jobs:
             CMAKE_OPTIONS="$CMAKE_OPTIONS -DENABLE_SWIFT=ON"
           elif ${{ inputs.os_name == 'Linux' }} ; then
             if ${{ inputs.toolchain == 'Clang' }} ; then
-              echo "host_cc=clang-19" >> "$GITHUB_OUTPUT"
-              echo "host_cxx=clang++-19" >> "$GITHUB_OUTPUT"
+              echo "host_cc=clang-20" >> "$GITHUB_OUTPUT"
+              echo "host_cxx=clang++-20" >> "$GITHUB_OUTPUT"
             elif ${{ inputs.toolchain == 'GNU' }} ; then
               echo "host_cc=gcc-14" >> "$GITHUB_OUTPUT"
               echo "host_cxx=g++-14" >> "$GITHUB_OUTPUT"
diff --git a/.github/workflows/libjs-test262.yml b/.github/workflows/libjs-test262.yml
index 95db15484bb..eaae10530af 100644
--- a/.github/workflows/libjs-test262.yml
+++ b/.github/workflows/libjs-test262.yml
@@ -51,10 +51,10 @@ jobs:
       - name: Install dependencies
         run: |
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-          sudo add-apt-repository 'deb http://apt.llvm.org/noble/ llvm-toolchain-noble-19 main'
+          sudo add-apt-repository 'deb http://apt.llvm.org/noble/ llvm-toolchain-noble-20 main'
 
           sudo apt-get update -y
-          sudo apt-get install -y ninja-build unzip clang-19 clang++-19 jq wget curl zip tar autoconf autoconf-archive automake nasm pkg-config libgl1-mesa-dev rsync
+          sudo apt-get install -y ninja-build unzip clang-20 clang++-20 jq wget curl zip tar autoconf autoconf-archive automake nasm pkg-config libgl1-mesa-dev rsync
 
           test -e /opt/wabt-1.0.35 || (
             cd /tmp
@@ -96,11 +96,11 @@ jobs:
           export HOME=${{ github.workspace }}/home
           mkdir -p $HOME
           env PATH="/opt/wabt-1.0.35/bin:$PATH" \
-            CC=clang-19 \
-            CXX=clang++-19 \
+            CC=clang-20 \
+            CXX=clang++-20 \
             cmake --preset CI -B libjs-test262/Build \
-              -DCMAKE_C_COMPILER=clang-19 \
-              -DCMAKE_CXX_COMPILER=clang++-19 \
+              -DCMAKE_C_COMPILER=clang-20 \
+              -DCMAKE_CXX_COMPILER=clang++-20 \
               -DWASM_SPEC_TEST_SKIP_FORMATTING=ON \
               -DINCLUDE_WASM_SPEC_TESTS=ON \
               -DENABLE_GUI_TARGETS=OFF
diff --git a/Documentation/BuildInstructionsLadybird.md b/Documentation/BuildInstructionsLadybird.md
index c3953a08253..7a46ddb8d4e 100644
--- a/Documentation/BuildInstructionsLadybird.md
+++ b/Documentation/BuildInstructionsLadybird.md
@@ -4,7 +4,7 @@
 
 Qt6 development packages, nasm, additional build tools, and a C++23 capable compiler are required.
 
-We currently use gcc-14 and clang-19 in our CI pipeline. If these versions are not available on your system, see
+We currently use gcc-14 and clang-20 in our CI pipeline. If these versions are not available on your system, see
 [`Meta/find_compiler.sh`](../Meta/find_compiler.sh) for the minimum compatible version.
 
 CMake 3.25 or newer must be available in $PATH.
@@ -52,10 +52,10 @@ sudo wget -O /usr/share/keyrings/llvm-snapshot.gpg.key https://apt.llvm.org/llvm
 # Optional: Verify the GPG key manually
 
 # Use the key to authorize an entry for apt.llvm.org in apt sources list
-echo "deb [signed-by=/usr/share/keyrings/llvm-snapshot.gpg.key] https://apt.llvm.org/$(lsb_release -sc)/ llvm-toolchain-$(lsb_release -sc)-19 main" | sudo tee -a /etc/apt/sources.list.d/llvm.list
+echo "deb [signed-by=/usr/share/keyrings/llvm-snapshot.gpg.key] https://apt.llvm.org/$(lsb_release -sc)/ llvm-toolchain-$(lsb_release -sc)-20 main" | sudo tee -a /etc/apt/sources.list.d/llvm.list
 
 # Update apt package list and install clang and associated packages
-sudo apt update -y && sudo apt install clang-19 clangd-19 clang-tools-19 clang-format-19 clang-tidy-19 lld-19 -y
+sudo apt update -y && sudo apt install clang-20 clangd-20 clang-tools-20 clang-format-20 clang-tidy-20 lld-20 -y
 ```
 
 - Alternative: Install gcc from [Ubuntu Toolchain PPA](https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test):
@@ -122,7 +122,7 @@ brew install autoconf autoconf-archive automake ccache cmake nasm ninja pkg-conf
 
 If you wish to use clang from homebrew instead:
 ```
-brew install llvm@19
+brew install llvm@20
 ```
 
 If you also plan to use the Qt UI on macOS:
diff --git a/Meta/Lagom/BuildFuzzers.sh b/Meta/Lagom/BuildFuzzers.sh
index 73118108769..a6d1e99ba2d 100755
--- a/Meta/Lagom/BuildFuzzers.sh
+++ b/Meta/Lagom/BuildFuzzers.sh
@@ -14,7 +14,7 @@ die() {
 
 pick_clang() {
     local BEST_VERSION=0
-    for CLANG_CANDIDATE in clang clang-17 clang-18 clang-19 /opt/homebrew/opt/llvm/bin/clang ; do
+    for CLANG_CANDIDATE in clang clang-17 clang-18 clang-19 clang-20 /opt/homebrew/opt/llvm/bin/clang ; do
         if ! command -v $CLANG_CANDIDATE >/dev/null 2>&1; then
             continue
         fi
diff --git a/Meta/find_compiler.sh b/Meta/find_compiler.sh
index c501d54793d..320a0814248 100644
--- a/Meta/find_compiler.sh
+++ b/Meta/find_compiler.sh
@@ -56,7 +56,7 @@ pick_host_compiler() {
         return
     fi
 
-    find_newest_compiler clang clang-17 clang-18 clang-19 /opt/homebrew/opt/llvm/bin/clang
+    find_newest_compiler clang clang-17 clang-18 clang-19 clang-20 /opt/homebrew/opt/llvm/bin/clang
     if is_supported_compiler "$HOST_COMPILER"; then
         export CC="${HOST_COMPILER}"
         export CXX="${HOST_COMPILER/clang/clang++}"